How effective are Pyarmor and Nuitka at preventing reverse engineering?

Honestly, unless you're implementing some cutting-edge algorithm, not many people will be interested in reverse engineering your code. Most developers simply don’t have the time or motivation unless they suspect malicious intent.

That said, even C can be reverse engineered. Tools like Ghidra are getting better at decompiling native code, so solid obfuscation is still key if you want to protect your work.

If you really want to protect your code, Python might not be the best choice. Languages like C, Golang, or Rust are generally harder to reverse engineer. Even if you encrypt your Python code, once it’s decrypted in memory, someone can still access it. It's a good idea to prototype in Python but then translate critical components into a more secure language.

I actually use Nuitka for this reason. It does make reverse engineering a lot harder, often more than it's worth for someone who would rather just pay for your software.